Devices are known for helping sport and commercial fisherman detect fish. One such device is a sonar transducer. Sonar transducers bounce sound waves off the sea bottom for detecting fish and other underwater objects, and provide a graphical output to a sophisticated monitor by use of heavy shielded cables. Fisherman must constantly watch the monitor for signs of underwater activity. This can be a time consuming chore and a distraction from the ultimate goal of catching fish.
Sonar transducers respond to the reflection of sound waves, and therefore must be fixed to the bottom of a ship or boat, or hung from the side of the boat to direct sound waves towards the sea bottom. The transducers along with a pre-amplifier are normally encased within hard rubber or plastic to form a waterproof enclosure, which adds to the size and weight of these devices. Due to the sophistication and complexity of these devices, they need to draw power off of the power supply of a ship or boat. This requires extensive time and labor to outfit a boat for and install these devices. On large boats, mounting of the transducer can require a diver to perform underwater installation or it can require the boat to be hauled out of the water for the work to be accomplished in dry dock.
The monitors associated with sonar transducers can take up large amounts of precious console space, which can be especially troublesome on small boats with limited room. Making room for the monitor is not an easy task; it may involve moving other electronic devices on the boat due to interfering signals, or adding housings to the boat for placement and separation of specific electronics.
Another type of acoustic device for detecting underwater activity is a hydrophone, which is generally no smaller than a fist. These devices are normally used for research expeditions, and are used in highly complex electronic systems. Hydrophones, like sonar transducers use large shielded cables, and are generally encased with a pre-amplifier in hard rubber or plastic to form a waterproof enclosure, which adds to the size and weight of these devices. Due to the size, weight, and cable requirements, hydrophones cannot be cast or attached to a fishing line or lure. They have limited mobility and are usually suspended from the side of a boat.
Hydrophones are also normally associated with sophisticated and expensive power amplifiers that are capable of amplifying specific frequencies and tones for detailed analysis of underwater activity. These power amplifiers are generally large and expensive, requiring tabletop space and use of a ship's power supply. The combination of large hydrophones, heavy cables and large power amplifiers, limits the portability of a hydrophone system. Even though hydrophone systems might be suitable for researchers, oceanographers, or some commercial fisherman, they are totally unsuitable for a sport fisherman.
Sport fisherman could benefit from a lightweight portable device that could help in the detection of underwater activity. A device that allows a fisherman, while fishing, to freely move about a boat or along the shore, bank, or a dock, without requiring constant monitoring of electronic equipment would be particularly advantageous. Small boat owners could additionally benefit from an underwater activity detection system that does not require precious boat space to be consumed. Shoreline or bank fisherman would be especially well served by such a device because there is no underwater listening device of any size, capability, or complexity that is suitable for shore-based applications. But presently no low cost, simple, small, lightweight, low power, easily operated device exits capable of detecting underwater activity of lures and fish, both near and far from a boat or shore.